Photoconductive bisphenyl thiocompounds linked by bridging organic group

ABSTRACT

A photoconductive composition useful in electrophotographic processes is provided by utilizing in admixture with an electrically insulating polymeric organic binder a monomeric organic photoconductor which is a bisphenylthio compound wherein at least one of the phenylthio residues carries a para-tertiary amino group and the two thio atoms are linked together by a bridging organic group which may be an aliphatic, atomatic or heterocyclic residue. Preferably, the two phenylthio residues carry similar paratertiary amino groups. The composition is used in the form of a photoconductive layer, either self-supported or carried on a support which may be paper or the like or a conductive surface, depending upon the manner of utilization. A fine powder of the composition containing a sensitizing dysestuff is useful in phototoner processes.

nite Sates Hectors Dec. 3, 1974 [22] Filed:

[ 1 PHOTQCONDUCTIVE BISPHENYL THIOCOMPOUNDS LINKED BY BRIDGING ORGANIC GROUP [75] Inventor: Adrianus Marie Petrus Hectors,

Venlo, Netherlands [73] Assignee: Oce-van der Grinten N.V., Venlo,

Netherlands May 14, 1971 [21] Appl. No.: 143,587

[30] Foreign Application Priority Data May 14, 1970 Great Britain 23484/72 [52] US. Cl 96/1.4, 96/1.5, 96/1.6, 252/621, 260/247.1, 260/247.5, 260/248 R, 260/249.5, 260/244.8 R, 260/294.80,

[51] Int. Cl. G03g 5/06, (303g 13/16, 603g 13/22 [58] Field of Search 96/1, 1 PC, 1.5, 1.4;v

[56] References Cited UNITED STATES PATENTS 2,351,657 6/1944 Bayes 260/247.l X

2,384,577 9/1945 Thomas 260/247.1 X 2,435,508 2/1948 Paul et al,.... 260/578.X 2,983,726 5/1961 Hendry 260/247.l 3,261,825 7/1966 Lesslie ct al. 260/578 X 3,299,040 1/1967 Jeremias et 260/578 X 3,388,126 6/1968 Harman 260/247.l

Primary Examiner-Roland E. Martin, Jr. Attorney, Agent, or Firm-Albert C. Johnston 5 7] ABSTRACT V toconductive layer, either self-supported or carried on a support which may be paper or the like or a conductive surface, depending upon the manner of utilization. A fine powder of the composition containing a sensitizing dysestuff is useful in phototoner processes.

15 Claims, N0 Drawings PHOTOCONDUCTIVE BISIPHENYL I THIOCOMPOUNDS LINKED BY BRIDGING ORGANIC GROUP electrophotographic processes for the production of copies.

In the most common process, the photoconductive coating is charged in the dark and exposed to light so as to produce a charge image, after which the charge image is made visible by the selective attraction of pigment (toner) particles to the charged areas. In direct electrophotography the toner particles are fixed onto the photoconductive coating, whereas in the indirect process the particles are transferred to a receiving support and fixed thereon.

In another process anuncharged photoconductive coating is imagewise exposed so as to produce a conductivity pattern which can be converted into a charge image ready to be developed with toner particles or can be developed by selective electrolytic deposition of coloring matter in accordance with the conductivity pattern.

Electrophotographic processes are also known in which photoconductive particles are attached to a sup port by electrostatic forces and image-formation is based on selective destruction of the electrostatic attraction. These are called phototoner processes.

The most familiar photoconductors are amorphous selenium and zinc oxide. Many other substances have been proposed, both organic and inorganic.

Organic photoconductors enable the formation of smooth and grainless layers, and thus are particularly useful for reproduction of fine details. Such photoconductors may be polymeric or non-polymeric. The polymeric' substances, such as polyvinylcarbazole, often vary batch by batch with regard to their photoconductive properties.

The known non-polymeric photoconductors, which genereally are used with electrically insulating binders, differ considerably as to chemical constitution and photoconductive behavior. While they relate to many and very different classes of compounds, those in which two phenyl nuclei are linked via a bridging member and at least one of the phenyl nuclei is p-amino-substituted ,show especially interesting properties. Among the tors of the formula:

(Y) n (Y1) m Rt 2 in which two phenyl nuclei, at least one of which carries an amino substituent in the p-position, are linked together by means of a bridging group X which consists of an element of group 6a of the Periodic Sys tem of Elements, a combination of similar or different elements of that group or, when the bridging group comprises selenium and/or tellurium, a combination of the same with a halogen; and in which formula: R, represents a hydrogen atom or an alkyl, aralkyl or cycloalkyl radical;

R represents an alkyl, aralkyl, cycloalkyl or aryl radical;

Z represents a hydrogen or halogen atom, an alkyl, alkoxy, acylamino, or sulfonamido radical or the group in which R represents a hydrogen atom or an alkyl, aralkyl or cycloalkyl radical and R, a hydrogen atom or an alkyl, aralkyl, cycloalkyl or aryl radical. Y and Y are similar or different and represent a halogen or an alkyl or alkoxy radical; and m and n each is equal to zero, 1 or 2.

Those non-polymeric photoconductors are highly useful when combined with an electrically insulating binder to provide a photoconductive coating composition. Such a composition on a suitably conductive support gives a material on which excellent copies can be made by electrophotographic reproduction.

Compounds according to the above formula in which the bridging group X consists of a plurality of identical atoms, such as S S Se or T62, have been found somewhat less light-sensitive than those in which the bridging group consists of a single S, Se or Te atom between the phenyl nuclei.

According to the present invention, new photoconductive compositions containing an organic photocon ductor and an electrically insulating binder are provided, in which the photoconductor is a monomeric compound having two phenylthio residues, at least one of which carries a tertiary amino group in the para position relative to its sulfur atom, which residues are linked together by means of an organic bridging group between the respective sulfur atoms. [t has been discovered that these compositions often exhibit lightsensitivity equal to or even greater than that ofthe similar compositions above mentioned in which the photoconductor contains a single sulfur atom as a bridge between two phenyl nuclei.

The photoconductors to be used according to the present invention are, more particularly, compounds having the general formula:

in which X represents an aliphatic, aromatic or hetero cyclic organic bridging group; R is an alkyl, cycloalkyl or aralkyl radical an R is an alkyl, cycloalkyl or aralkyl radical, or R and R together with the nitrogen atom to which they attach form a saturated heterocyclic ring; and

Z is a hydrogen or halogen atom, an alkyl or alkoxy :8

radical or an amino group in which R and R each is a hydrogen atom or an alkyl, cycloalkyl or aralkyl group, or R and R together with the nitrogen atom to which they attach form a saturated heterocyclic ring.

The compounds in which Z is an amino group and R and R have the same structures as R, and R are preferred because they are simpler to synthesize.

When the organic bridging group X of the formula is an aliphatic radical, it may be alkylene residue, (C- H an alkenylene residue, (CH=CH )m or [(CH -),,(Cl-l=CH) -(CH an aliphatic dicarboxylic residue, e.g., CO(CH ),,.CO or CO-(CH=CH) CO-, or a cycloaliphatic group, whether or not containing one or more hetero atoms. Each of the variables n, m and s represent an integer ranging from I upwards, and each of the variable p, q, r, k and 1 represents either zero or an integer ranging from I upwards with the sum of p, q and r being an integer. The ranges of these integers do not have critical upper limits but for practical reasons, such as solubility, they do not exceed values of approximately 10.

When the bridging group X is aromatic, it may be an isocyclic aromatic radical, such as a phenylene, polyphenylene 0r naphthylene radical or another condensed ring system, or an aromatic dicarboxylic residue (e.g. of formula CO-C H CO-), or a heterocyclic aromatic radical such as a pyridine, (s)-triazine, furane, pyrrol or thiophene group.

Among the compounds which are preferred and especially useful for the purposes of this invention are those which meet the general formula:

in which each phenyl residue either is non-substituted or may carry one or more of usual substituents such as an alkyl or alkoxy group or a halogen atom and in which X and R have the meanings indicated in the fol lowing tabulation:

Sensitizers and activators canbe added to the photo conductive compositions of the invention in the conventional way; Examples of dyestuffs suitable for use in them as sensitizers are set-forth in the aforesaid copending application Ser. No. 9,061. Substances useful in them as activators are disclosed in Belgian Pat. No. 570,790.

The monomeric photoconductors herein specified are used in combination with insulating polymeric binders. Among such'binders that may be used effectively are, for example, plasticized or unplasticized silicon resins, polystyrene, polyacrylic or polymethacrylic esters, colophony resins, chlorinated rubbers, polyvinyl chloride, polyvinyl acetate, vinyl chloride/acetate copolymers, polyvinyl acetals, phenolformaldehyde resins, polyamides, polyesters, cellulose esters, cellulose ethers and alkyd resins or mixtures thereof.

The photoconductive compositions herein disclosed may be used in the form of a photoconductive layer, which may be either self-supporting or coated on a suit able support, or may be used in a so-called phototoner process in the form of a powder having more or less spherical particles. They may be coated on flexible or rigid supports such as of metal, paper, metallized plastic foil ornesa glass, so as to provide valuable electrophotographic materials. The specified photoconductors can be used in them individually or mixtures of different compounds of the nature specified or with photoconductors of other constitution.

The photoconductors herein disclosed are sensitive to light of wavelength shorter than 3,000 A. Most of them are almost colorless, i.e., highly transparent to visible radiation in the range above 3,000 A. Nevertheless they show excellent sensitivity for visible light when used in admixture with a suitable sensitizing dye and/or activator. It is indeed surprising that these relatively simple and easily producible compounds have not been previously proposed for use as photoconductors, for their properties fulfill the requirements to be met by organic photoconductors.

The electrophotographic layers provided according to the present invention are suitable for carrying out conventional electrophotographic processes, such as those in which a photoconductive layer is charged, i magewise exposed and developed and those in which copying is based on a conductivity image resulting from imagewise exposure without a previous or simultaneous charging step. In the latter processes the conductivity image is converted into a ready developable charge image or is developed by electrolytic deposition of coloring matter which may be a powder or a liquid developer. The developed visible image can be fixed directly on the photoconductive surface or can be transferred: onto a receptor surface and fixed'thereon.

The electrophotographic materials of the present invention, i.e., the materials which comprise a support and a layer thereon of a photoconductive composition herein disclosed, can be used for making single copies and also for the production of transparent copies such as microcopies, micrates or intermediate copies for overhead projection or for further reproduction, e.g. on diazotype paper. Furthermorethe new photoconductive compositions can be applied to suitable supports to make electrophotographic plates for planography, for relief or intaglio printing, or for the production of masters for spirit duplicating or for xeroprinting.

The photoconductive compositions are also useful for the formation of a photoconductive layer to'be employed in copying-duplicating machines which make use of the indirect electrophotographic process. A pho toconductive layer made from such a composition can be used in combination with other photoconductive or semiconductor layers, e.g. with a layer containing CdS or Se.

The preparation of the compounds to be used as photoconductors according to the present invention can be effected by processes readily practicable by chemists skilled in organic reactions. These compounds may be prepared either by bringing a p-tertiary amino-phenylmercaptan into reaction with an organic di-halogen compound, or by reacting a p-halogen nitrobenzene with an organic dithiol, and subsequently reducing and alkylating or arylating the reaction product.

The practice of the invention will be further-evident from the following illustrative examples.

EXAMPLE I A paper support is coated with a solution of 20 g of polyvinyl chloride/acetate 2 g of l.2-bis[4-N.N-diethyl umino-phunyl-thio|- ethenc and 0.07 g of Rhodamine B extra in 150 ml of acetone.

After drying a coating of about 5 g/m in weight is obtained.

The electrophotographic paper thus made is charged negatively and then is placed in contact with a photographic diapositive and exposed through it for 5 seconds to light from an incandescent lamp of 40W at a distance of cm. The latent image thus formed is de veloped by applying positively charged toner particles to it with the aid of a magnetic brush, and the developed image is fixed by heating. A clear positive copy of the diapositive results.

EXAMPLE ll A paper support is coated with a solution of of a polyvinyl chloride/acetate of l.2his[4-N.N-dihenzyl amino phenyl thiolethene and of Rhodamine B extra in of. chloroform.

After drying the coating the paper carries a layer of 5 g/m A copy is produced in the way described in Example I.

EXAMPLE III A copy is produced in the way described in Example I, excepting that the coating solution used contains 1,2- bis[4-N-methyl-N-cyclopentyl-amino phenyl thio] eth ene as the photoconductor and acetone as the solvent.

EXAMPLE IV A coating is formed on paper by applying to the paper a solution of It) g olpolyvinyl chloride H) g ml a modified colophonium resin ol' I.lLhis-l4-N,N-diuthylamino phcnyl lhiol dichloroethcne and of Rhodamione 8 extra in of acetone 0.07 g ISO ml and drying the coating.

Copying is effected as described in Example I, and a clear positive copy results.

EXAMPLES V XIII Copies were produced in the manner described in Example I on electrophotographic materials obtained by coating paper with solutions containing the following substances as organic photoconductors and insulating binders:

wherein R, and R each represents a lower alkyl radical, a 5- or 6-membered cycloalkyl radical or an aryllower alkyl, or R and R together with the nitrogen atom to which they attach form a morpholine ring; Z represents a hydrogen or halogen atom, a lower alkyl or lower alkoxy radical, or an amino group in which R and R each represents a hydrogen atom, a lower alkyl radical, a 5- or 6-membered cycloalkyl radical or an aryl-lower alkyl, or R and R together with the nitrogen atom to which they attach form a morpholine ring; and X is a lower aliphatic or an aryl phcnylthiol-thiosuccinate EXAMPLE XIV A solution is made of one part by weight of l,2-bisl 4- N,N-diethylamino-phenylthiol-ethene and 5 parts by weight of polyvinyl chloride/acetate in acetone. A

small amount of the dyestuff Rhodamine B extra is added as a sensitizer. The acetone then is evaporated off and the residue is milled to a powder of approximately ,u. particle size.

The powder particles are applied to a conductive plate in a uniform layer and subsequently charged by a negative corona-discharge. Upon imagewise exposure of the charged powder layer to light the particles in exposed areas of the layer lose their charge and then are easily removed selectively from the plate. The remnant powder image is transferred from the plate onto a receptor paper by use of an electrostatic field, and is fixed on the paper to provide a permanent copy of the original image.

The present invention is not to be considered restricted to particulars of the compounds, materials, processes or examples hereinabove described except as may be required by fair interpretation of the appended claims.

I claim:

l. A photoconductive composition comprising in admixture with an electrically insulating polymeric organic binder a monomeric organic photoconductor which is a compound having the formula:

modified colophonium resin radical or a heterocyclic residue containing at least one nitrogen, oxygen or sulfuration.

2. A photoconductive composition according to claim 1, wherein x is an aliphatic residue selected from the group consisting of alkylene. alkenylene, aliphatic dicarboxylic and cycoaliphatic residues.

3. A photoconductive composition according to claim 1, wherein X is an aromatic residue selected from the group consisting of anthryl, phenylene polyphenylene, naphthylene, dicarboxylic phenyl, pyridine, furane, pyrrol, thiophene and triazine residues.

4. A photoconductive composition according to claim 3 wherein Z is said amino group 5. A photoconductive composition according to claim 4 wherein Z is said amino group 6. A photoconductive composition according to claim 1 wherein said photoconductor is selected from the group consisting of l,Z-bisl4-N,N-diethyl-aminophenylthiol-ethene, 1,2-bisl 4-N,N-dibenzylaminophenylthiolethene, 1.2-bisl4-N-methyl-N- cyclopentylamino-phenylthiolethene, l,2-bis[4-N,N- diethylamino-phenylthiol-dichloroethene, l,4-bis l4- N,N-diethylamino-phenylthio]-butane, I ,2-bisl 4-N- butyl-N-benzyl-amino-phenylthio]-ethene, l.2-bisl4- N(H)cyclohexyl aminophenylthio]ethene, l,2- bis[4- morpholinophenylthiol-ethene. l,4-his[ 4'-N,N-

9 diethylamino-phenylthiol phenylene', 2,6-bis[4-N,N-

diethylamino-phenylthio]-aniline, bis [4-N,N-diethylamino-phenylthiol-thion, bis[4-N,N-diethylaminophenylthio]-thiolsuccinate, l,2-bis[4-N,N- dimethylamino-Z-methyl-phenylthiol-ethene and 1,2- bis[4-N,N-diethylamino-phenylthiolethane.

7 An electrophotographic material comprising a layer of a photoconductive composition according to claim 1.

8. An electrophotographic material comprising a support having substantial electrical conductivity and carrying thereon a layer of a photoconductive composition according to claim 1.

9. An electrophotographic material comprising a paper support carrying thereon a layer of a photoconductive composition according to claim 1.

10. An electrophotographic material comprising a photoconductive composition according to claim 1 in the form of a fine powder useful as a photoconductive toner.

' 11. An electrophotographic material according to claim 10, said powder having an average particlesize of the order of approximately microns.

12. The process of producing an electrophotographic copy which comprises electrostatically charging a layer of a photoconductive composition according to claim ll, imagewise exposing the charged layer to light, and thereafter applying oppositely charged toner particles to said layer and fixing said particles to the unexposed image areas thereof.

13. The process of producing an electrophotographic copy which comprises applying to an electrically conductive. surface a layer of a fine powder the particles of which contain a photoconductive composition according to claim 1 with a sensitizing dyestuff, electrostatically charging said layer, then imagewise exposing it to light, removing from said surface the powder in the ex-.

posed image areas of said layer, and transferring from 14. A photoconductive composition comprising in admixture with an electrically insulating polymeric organic binder a monomeric organic photoconductor having the formula:

in which R and R each is a hydrogen atom, an alkyl radical having 1 to 4 carbon atoms, a 5- or 6-membered cycloalkyl radical or a benzyl radical, or R and R together with the nitrogen atom to which they attach form' a morpholine ring; and X is a residue selected from the group consisting of alkylene, lower alkenylene, aliphatic dicarboxylic and cycloaliphatic residues. aryl or aryl dicarboxylic residues, and heterocyclic aromatic residues containing at least one nitrogen. oxygen or sulfur atom.

15. A photoconductive composition according to claim 1, wherein Z is an amino group in which R and R, correspond to R and R and X is 

1. A PHOTOCONDUCTIVE COMPOSITION COMPRISING IN ADMIXTURE WITH AN ELECTRICALLY INSULATING POLYMERIC ORGANIC BINDER A MONOMERIC ORGANIC PHOTOCONDUCTOR WHICH IS A COMPOUND HAVING THE FORMULA:
 2. A photoconductive composition according to claim 1, wherein x is an aliphatic residue selected from the group consisting of alkylene, alkenylene, aliphatic dicarboxylic and cycoaliphatic residues.
 3. A photoconductive composition according to claim 1, wherein X is an aromatic residue selecteD from the group consisting of anthryl, phenylene polyphenylene, naphthylene, dicarboxylic phenyl, pyridine, furane, pyrrol, thiophene and triazine residues.
 4. A photoconductive composition according to claim 3 wherein Z is said amino group
 5. A photoconductive composition according to claim 4 wherein Z is said amino group
 6. A photoconductive composition according to claim 1 wherein said photoconductor is selected from the group consisting of 1,2-bis(4-N,N-diethyl-amino-phenylthio)-ethene, 1,2-bis(4-N,N-dibenzylamino-phenylthio) ethene, 1,2-bis(4-N-methyl-N-cyclopentylamino-phenylthio)ethene, 1,2-bis(4-N,N-diethylamino-phenylthio)-dichloroethene, 1,4-bis (4''-N,N-diethylamino-phenylthio)-butane, 1,2-bis(4-N-butyl-N-benzyl-amino-phenylthio)-ethene, 1,2-bis(4-N(H)cyclohexyl aminophenylthio)-ethene, 1,2-bis(4-morpholinophenylthio)-ethene, 1,4-bis(4''-N,N-diethylamino-phenylthio) phenylene, 2,6-bis(4''-N,N-diethylamino-phenylthio)-aniline, bis (4-N,N-diethyl-amino-phenylthio)-thion, bis(4-N,N-diethylamino-phenylthio)-thiolsuccinate, 1,2-bis(4-N,N-dimethylamino-2-methyl-phenylthio)-ethene and 1,2-bis(4-N,N-diethylamino-phenylthio)ethane.
 7. An electrophotographic material comprising a layer of a photoconductive composition according to claim
 1. 8. An electrophotographic material comprising a support having substantial electrical conductivity and carrying thereon a layer of a photoconductive composition according to claim
 1. 9. An electrophotographic material comprising a paper support carrying thereon a layer of a photoconductive composition according to claim
 1. 10. An electrophotographic material comprising a photoconductive composition according to claim 1 in the form of a fine powder useful as a photoconductive toner.
 11. An electrophotographic material according to claim 10, said powder having an average particle size of the order of approximately 20 microns.
 12. The process of producing an electrophotographic copy which comprises electrostatically charging a layer of a photoconductive composition according to claim 1, imagewise exposing the charged layer to light, and thereafter applying oppositely charged toner particles to said layer and fixing said particles to the unexposed image areas thereof.
 13. The process of producing an electrophotographic copy which comprises applying to an electrically conductive surface a layer of a fine powder the particles of which contain a photoconductive composition according to claim 1 with a sensitizing dyestuff, electrostatically charging said layer, then imagewise exposing it to light, removing from said surface the powder in the exposed image areas of said layer, and transferring from said surface to and fixing on a receiving support the powder remaining in the unexposed image areas of said layer.
 14. A photoconductive composition comprising in admixture with an electrically insulating polymeric organic binder a monomeric organic photoconductor having the formula:
 15. A photoconductive composition according to claim 1, wherein Z is an amino group 